The 2.6V6 has a very large number of vacuum hoses (circa 24), a leak or constriction or incorrect connection causes hard to locate problems.
Vacuum leaks, even tiny ones, cause a rough idle and often stalling at traffic lights and such like. Remove the oil dipstick when the engine is running to see what a vacuum leak is like.
Around 5 metres of hose is required (EGR Valve, EGR Vent, EGR Vacuum, VRIS1, VRIS2, Purge Control, PRC, Cruise-Control, Fuel Pressure Regulator and Airbox). Thus the choice of black rubber is useful at making the black hole an entangling web... can take days to get entrapped mechanics out.
Silicone Hose Supplier
A supplier of high-temperature long-life Silicone Vacuum Hoses is Samco, available in various colours (blue/red/yellow) and sizes. For vacuum hoses the application is 3mm bore, 2mm wall. Silicone easily tolerates the 95oC underhood temperatures and 130oC temperatures by the EGR Vent/Vacuum solenoid area. Price is around £1.90 from Demon Tweaks in the UK, who supply it in 3 metre lengths, or around 1.50$US per metre (+44 (0)1978 664466).
To replace all hoses, remove one hose at a time, measuring the new hose to fit. The VRIS1, VRIS2, EGR Vent, EGR Vacuum, EGR Valve, Purge hoses are difficult to replace and are T-pieced & Y-pieced off one another.
With time the EGR Solenoid & EGR Valve vacuum hoses will be baked onto the fittings and very difficult to remove, extreme care must be exercised if the plastic solenoid fittings are not to be damaged. If one is broken one it may be possible to superglue the sheared tube-fitting back on and then araldite epoxy around it to achieve a sealed & mechanically strong repair, if not they are around 45$US each (Roebuck).
EGR Vacuum & EGR Vent solenoids are down behind the back of the engine, attached as a pair to a plate which is secured by two 10mm nuts to two engine fitted studs. It is strongly suggested to remove this plate before replacing these hoses. Access is via each of the engine by feel with a 10mm spanner and fingers-backing nuts off. The airbox and tube after it pre-Throttle-Body must be removed also, taking care not to damage the VAF.
Benefits of replacing Vacuum Hoses
Replacing hoses often solves long-standing rough idle and lost 4k-rpm turbo-kick on V6s. Silicone tolerates heat far better which eliminates the need to ever perform the procedure a second time or before skin-grafts heal.
It is worth checking the hoses from the EGR solenoid hose that curve down to the EGR valve (on top of the back part of the engine/transmission interface), as it can easily be pinched off due to heat & being too short.
The orientation of Vacuum Hoses is shown below, excluding those for Cruise Control unit. Those fitting aftermarket filters should tap the hose at the back of the airbox into the new filter (use a windscreen-washer L or in-line piece from an auto supply), otherwise the car will stall at idle-stops.